这个项目的目标是创建一个API，它每小时刷新一次，为我将每小时从互联网上抓取的游戏列表提供最新的投注赔率。返回的JSON的目标结构将是每个游戏作为父对象，嵌套的子对象将是按更新日期刮取的每个划线器的前1条记录。我的理解是，实现这一点的最佳方法是修改ListSerializer中的to_representation函数，以返回适当的查询集。
因为我需要父元素的game_id来获取相应游戏的子元素，所以我尝试从传递的数据中提取game_id。问题是，当我通过异常看到这一行包含的内容时，它看起来是正确填充的，但当我让完整的代码运行时，我会得到一个列表索引超出范围的异常。
例如
class OddsMakerListSerializer(serializers.ListSerializer):
def to_representation(self, data):
game = data.all()[0].game_id
#if I put this here it evaluates to 1 which should run the raw sql below correctly
raise Exception(game)
data = OddsMaker.objects.filter(odds_id__in = RawSQL(''' SELECT o.odds_id
FROM gamesbackend_oddsmaker o
INNER JOIN (
SELECT game_id
, oddsmaker
, max(updated_datetime) as last_updated
FROM gamesbackend_oddsmaker
WHERE game_id = %s
GROUP BY game_id
, oddsmaker
) l on o.game_id = l.game_id
and o.oddsmaker = l.oddsmaker
and o.updated_datetime = l.last_updated
''', [game]))
#if I put this here the data appears to be populated correctly and contain the right data
raise Exception(data)
data = [game for game in data]
return data
现在，如果我删除这些引发异常，我会得到列表索引超出范围。我最初的想法是，还有其他东西取决于"数据"作为列表返回，所以我创建了列表理解片段，但这并不能解决问题。
所以，我的问题是1(有没有更简单的方法来实现我的目标？我没有使用postgres后端，所以我无法使用它。2(如果没有，我不清楚传入的实例是什么，或者期望返回什么。我查阅了文档，看起来似乎需要一个字典，这可能是问题的一部分，但错误消息再次引用了一个列表。https://www.django-rest-framework.org/api-guide/serializers/#overriding-序列化和反序列化行为
我很感激你能提前了解这里发生了什么。
编辑：其余的序列化程序：
class OddsMakerSerializer(serializers.ModelSerializer):
class Meta:
list_serializer_class = OddsMakerListSerializer
model = OddsMaker
fields = ('odds_id','game_id','oddsmaker','home_ml',
'away_ml','home_spread','home_spread_odds',
'away_spread_odds','total','total_over_odds',
'total_under_odds','updated_datetime')
class GameSerializer(serializers.ModelSerializer):
oddsmaker_set = OddsMakerSerializer(many=True, read_only=True)
class Meta:
model = Game
fields = ('game_id','date','sport', 'home_team',
'away_team','home_score', 'away_score',
'home_win','away_win', 'game_completed',
'oddsmaker_set')
models.py:
class Game(models.Model):
game_id = models.AutoField(primary_key=True)
date = models.DateTimeField(null=True)
sport=models.CharField(max_length=256, null=True)
home_team = models.CharField(max_length=256, null=True)
away_team = models.CharField(max_length=256, null=True)
home_score = models.IntegerField(default=0, null=True)
away_score = models.IntegerField(default=0, null=True)
home_win = models.BooleanField(default=0, null=True)
away_win = models.BooleanField(default=0, null=True)
game_completed = models.BooleanField(default=0, null=True)
class OddsMaker(models.Model):
odds_id = models.AutoField(primary_key=True)
game = models.ForeignKey('Game', on_delete = models.CASCADE)
oddsmaker = models.CharField(max_length=256)
home_ml = models.IntegerField(default=999999)
away_ml = models.IntegerField(default=999999)
home_spread = models.FloatField(default=999)
home_spread_odds = models.IntegerField(default=9999)
away_spread_odds = models.IntegerField(default=9999)
total = models.FloatField(default=999)
total_over_odds = models.IntegerField(default=999)
total_under_odds = models.IntegerField(default=999)
updated_datetime = models.DateTimeField(auto_now=True)
views.py:
class GameView(viewsets.ModelViewSet):
queryset = Game.objects.all()
serializer_class = GameSerializer
感谢
要回答标题中的问题：
传递给Serializer.to_representation()的instance是初始化序列化程序时传递的实例
queryset = MyModel.objects.all()
Serializer(queryset, many=True)
instance = MyModel.objects.all().first()
Serializer(data)
通常你不必从ListSerializer本身继承。你可以从BaseSerializer继承，只要你在初始化过程中传递many=True，它就会自动"变成aListSerializer"。你可以在这里看到这个动作
回答您的问题
from django.db.models import Max
class OddsMakerListSerializer(serializers.ListSerializer):
def to_representation(self, data): # data passed is a queryset of oddsmaker
# Do your filtering here
latest_date = data.aggregate(
latest_date=Max('updated_datetime')
).get('latest_date').date()
latest_records = data.filter(
updated_date_time__year=latest_date.year,
updated_date_time__month=latest_date.month,
updated_date_time__day=latest_date.day
)
return super().to_representation(latest_records)